1113 Radiofrequency Ablation of Idiopathic Left Anterior Fascicular Tachycardia FRANK BOGUN, M.D., RAFEL EL-ATASSI. M.D., EMILE DAOUD, M.D., K. CHING MAN, D.O., S. ADAM STRICKBERGER, M.D., and ERED MORADY, M.D. From the Department of Internal Medicine, Division of Cardiology, The University of Michigan Medical Center, Ann Arbor, Michigan Left Anterior Fascicular Tachycardia. Introduction: A 45-year-oId man with idio- pathic ventricular tachycardia (VT) having a right bundle branch block configuration with right-axis deviation underwent au electrophysiologic test. Methods and Results: Mapping demonstrated a site ou the auterobasal wall of the left ventri- cle where there was an excelleut pace map and an endocardial activation time of -20 msec, hut radiofrequency catheter ahlation at this site was unsuccessful. At a nearhy site, a presumed Purkinje potential preceded the QRS complex by 30 msec during VT and sinus rhythm, and catheter ahlation was effective despite a poor pace map and an endocardial ventricular activa- tion time of zero. Conclusion: Idiopathic VT with a right hundle hranch configuration and right-axis devia- tion may originate in the area of the left anterior fascicle. A potential presumed to represent a Purkinje potential may he more helpful than endocardial ventricular activation mapping or pace mapping in guiding ablation of this type of VT. (J Cardiovasc Electrophysiol. Vol. 6, pp. 1113-1116, December 1995} Purkinje potential, pace mapping, ventricular tachycardia Introduction Idiopathic left ventricular tachycardia (VT) with a right bundle branch block configuration and left- axis deviation has been demonstrated to arise from the left posterior fascicle.' While a previous study suggested that idiopathic left VT with right-axis deviation may originate in the left anterior fasci- cle,-^ evidence supporting tliis possibility has been lacking. The purpose of the present case report is to demonstrate that idiopathic left VT may arise from the area of the left anterior fascicle. Case Presentation A 45-year-oid man was referred to the Uni- versity of Michigan Medical Center for tnanage- Dr. Boguri was supported by a grant from the Deutsche Forscliungsgemeinschaft. Address for correspondence: Fred Morady. M.D.. University of Michigan Medical Center. 1500 East Medical Center Dr.. B1F245. Ann Arbor, Ml 48109-0022. Fax: 313-936-7641. Manuscript received 8 August 1995; Accepted for publication 18 September 1995. ment of recurrent VT with a rate of 240 beats/min, a right bundle brancb block configuration, and right-axis deviation. TTie patient experienced symp- toms of rapid palpitations, iightheadedness, chest discomfort, and weakness during episodes of VT; there was no histoty of syncope. When VT first occurred 5 years earlier, he was treated with 480 mg/day of verapamil, which suppressed re- currences of VT for 1 year. However, in the 4 years prior to referral, nine episodes of sustained VT ne- cessitating visits to an emergency room for treat- ment with intravenous verapamil or electrical car- dioversion occurred. In the year prior to referral, he was treated with 540 mg/day of verapatnil. with three recurrences of sustained VT. These episodes of VT all had the same configuration: right bun- dle branch block with right-axis deviation. The physical exainination and ECG during sinus rhythm were normal, and there was no evidence of stiTic- tural heart disease detected by echocardiography or coronjiry angiography. After informed consent was obtained, an elec- trophysiologic procedure was performed 48 hours after discontinuation of tberapy with verapatnil.